1. Field of the Invention
The present invention relates to a radio communication system and method and a mobile communication terminal device, and more particularly, is applicable to a code division multiple access (CDMA) cellular telephone system.
2. Description of the Related Art
Data transmissions using cellular telephone systems have been limited to computer communications executed by individual users using facsimile or modems, and there have been no information providing services for providing various information through a cellular network. This is partly because the cellular telephone system does not have a sufficient communication capacity. That is, all existing cellular telephone systems can do is to provide call services, and they do not have an extra communication capacity for providing other services.
In the United States, attempts are being made to standardize the CDMA cellular telephone system to initiate its services. The CDMA method has been used in new mobile communication systems such as personal communication service (PCS) systems, and it has been firmly believed that in the United States, this method will be most popular during the next generation.
The CDMA method is characterized by its communication capacity that is much larger than that of the conventional frequency division multiple access (FDMA) method. In the future, half or more of the 25 MHz frequency band assigned to existing cellular telephone systems and the 60 MHz frequency band assigned to the PCS system can be operated by the CDMA method to obtain a communication capacity about ten times as large as that of conventional methods. Thus, for CDMA cellular telephone systems, call services do not use up all the assigned frequency bands, and this system is expected to provide value-added services such as information provision.
The CDMA system has a large communication capacity, but its capacity is still smaller than that of cable communication networks. The communication capacity of the cable system can be increased easily by increasing the number of cables, whereas the code multiplexing capability and the number of frequency bands for the CDMA method are limited. Thus, the CDMA cellular telephone system must be efficient in providing services.
In addition, minimizing the charge for receiving services is important in spreading the services, so the amount of information that can be provided per frequency is desirably maximized to efficiently provide services.
In view of the foregoing, objects of this invention are to provide a radio communication system and method and a mobile communication terminal device which can efficiently provide information services.
The foregoing objects and other objects of the invention have been achieved by the provision of a radio communication system and method and a mobile communication terminal device, wherein if various information is provided to the mobile communication terminal device separately from call services, update information on the information to be provided is transmitted from a base station, and the mobile communication terminal device receives the update information to examine whether or not the desired information has been updated, and if so, receives the desired information.
Since the update information is transmitted as described above, the mobile communication terminal device can easily examine whether or not the information to be provided has been updated. If whether or not the information has been updated can be determined, the information can be received only when it has been updated, and there will be no need to receive unwanted information or to connect to an information service center. Consequently, efficient information provision services can be provided.
In addition, according to the present invention, information to be transmitted using a code channel exclusively used to provide information is scrambled. Since information to be provided is scrambled, it can be received only by authorized mobile communication terminal devices.
In addition, according to the present invention, frequently received information is repeatedly transmitted by using the exclusive information-providing code channel while infrequently received information is transmitted by using a traffic channel by connecting the mobile communication terminal device and the information service center that provides information. And as update information, an index packet is transmitted, which includes the type of information to be provided, the version number of the information, and identification information that identifies whether the information is repeatedly transmitted by using the exclusive information-providing code channel or is transmitted by connecting to the information service center. The mobile communication terminal device examines whether or not the desired information has been updated, and if so, receives the exclusive information-providing code channel or connects to the information service center in order to obtain the desired information. Since frequently received information is transmitted through the exclusive information-providing channel while infrequently received information is transmitted by connecting to the information service center, the radio channels can be efficiently used to provide information, thus efficient information provision services as required can be provided.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.